The Characteristics of Atmospheric Ice Nuclei Measured at Different Altitudes in the Huangshan Mountains in Southeast China

The concentration of ice nuclei （IN） and the relationship with aerosol particles were measured and analyzed using three 5-L mixing cloud chambers and a static diffusion cloud chamber at three altitudes in the Huangshan Mountains in Southeast China from May to September 2011.The results showed that the mean total number concentration of IN on the highest peak of the Huangshan Mountains at an activation temperature （Ta） of-20℃C was 16.6 L-1.When the supersaturation with respect to water （Sw） and with respect to ice （Si） were set to 5％,the average number concentrations of IN measured at an activation temperature of-20℃C by the static diffusion cloud chamber were 0.89 and 0.105 L-1,respectively.A comparison of the concentrations of IN at three different altitudes showed that the concentration of IN at the foot of the mountains was higher than at the peak.A further calculation of the correlation between IN and the concentrations of aerosol particles of different size ranges showed that the IN concentration was well correlated with the concentration of aerosol particles in the size range of 1.2-20 μtm.It was also found that the IN concentration varied with meteorological conditions,such as wind speed,with higher IN concentrations often observed on days with strong wind.An analysis of the backward trajectories of air masses showed that low IN concentrations were often related to air masses travelling along southwest pathways,while higher IN concentrations were usually related to those transported along northeast pathways.

A Study of Supersaturation Spectra of Deposition Ice Nuclei

Ice nuclei-supersaturation spectra in the form of a Power Law ( Ni=RSir; B and y are empirical constants) have been expressed since 1973 when the curve was first introduced independentally by Gagin and Huffman. Experiments performed with a thermal gradient diffusion chamber in order to investigate the validity of the power curve. The results show that a linear curve fit to the data is as good as the power curve. The linear curve has the coefficients of correlation between 0.75 and 0.93 whereas the power curve fit to the same data has the coefficients between 0.82 and 0.93. The data reported by other workers, Zamurs and Jiusto and Zamurs et al., exhibit the same trend.

Numerical Analysis of Effects of Atmospheric Ice Nuclei Concentrations on Radiant Properties of Cold Clouds

Numerical simulations of 18 precipitation days from June to September in 1996with the 3D convective cloud model of CAMS (Chinese Academy of Meteorological Sciences, Version2000) were conducted. In these simulations, the concentration of IN (ice nuclei) was assumed toincrease by 5 times. The results show that when IN concentrations increase, the amounts ofprecipitation decrease, cloud tops heighten and the areas of cloud tops increase in 80 percentsimulated clouds. Moreover, in 95 percent simulated clouds, the sizes of ice crystals in cloudsdecrease and quantities increase. These results mean that the physical properties of clouds willchange when IN concentration increases. The radiant properties of clouds and climate may also changedirectly and indirectly.

A 2M^3 ISOTHERMAL CLOUD CHAMBER FOR THE STUDY OF ARTIFICIAL ICE NUCLEI

A 2m^3 isothermal cloud chamber mainly for ice nucleation research is described in this paper.Its structure, attached instruments and experimental procedures are also presented.The experiments of determining the ice nuclei effectiveness for the Agl-containing aerosols produced by three formulations have been conducted and the results have been compared with those of the CSU 960-liter isothermal cloud chamber.All experimental results show that the chamber has advantages of stable performance and reproducibility.It would be expected to become a useful experimental facility for ice nucleation research.

Multiyear Observations of Deposition-Mode Ice Nucleating Particles at Two High-Altitude Stations in India

Ice nucleating particle(INP) measurements were made at two high-altitude stations in India. Aerosols collected on filter paper at Girawali Observatory, Inter University Center for Astronomy & Astrophysics(IGO), and at the Radio Astronomy Center, Ooty(RAC), were activated in deposition mode using a thermal gradient diffusion chamber to determine the INP concentrations. The measurement campaigns at IGO were conducted during 2011, 2013 and 2014, and at RAC during 2013 and 2014. When the aerosol samples were exposed to an ice supersaturation of between 5% and 23% in the temperature range-17.6?C to-22?C, the maximum INP number concentration at IGO and RAC was 1.0 L-1and 1.6 L-1, respectively.A maximum correlation coefficient of 0.76 was observed between the INP number concentration and ice supersaturation. The airmass trajectories analyzed for the measurement campaigns showed that the Arabian Desert and arid regions were the main INP contributors. Elemental analysis of particles showed the presence of Na, Cl, Si, Al, Fe, Cu, Co, Cd, S, Mn and K, as well as some rare-Earth elements like Mo, Ru, La, Ce, V and Zr. When aerosols in the size range 0.5–20 μm were considered, the fraction that acted as INPs was 1 : 104to 1 : 106at IGO, and 1 : 103to 1 : 104at RAC. The higher ratio of INPs to aerosols at RAC than IGO may be attributable to the presence of rare-Earth elements observed in the aerosol samples at RAC, which were absent at IGO.

Marine biogenic aerosols and their effects on aerosol-cloud interactions over the Southern Ocean:a review

The Southern Ocean(SO)plays an important role in the global climate system.Changes in SO biogeochemistry and marine ecosystems may influence the distribution of atmospheric aerosols and clouds and impact the climate system.We reviewed current knowledge on the interactions between marine aerosols and clouds over the SO.We focused on marine primary and secondary organic aerosols and summarized their characteristics,processes and roles as cloud condensation nuclei and ice nuclei.We described in detail the interactions between the marine ecosystem,aerosols and clouds.We discussed marine productivity,formation of marine biogenic aerosols and interactions between aerosols,clouds and climate.We explored the impact of climate change on SO marine ecosystem productivity and aerosol-cloud-climate feedback.Marine biogenic aerosols could impact the radiation budget and oceanic low-level clouds over the SO.This study contributes towards an improved understanding of marine productivity,aerosol-cloud interactions and climate change in the SO.The SO may respond to climate change in varying degrees.More studies are urgently needed to support accurate forecasts of future changes in the SO.

THE STUDY OF HIGH EFFICIENT AgI PYROTECHNICS AND THEIR NUCLEATING PROPERTIES

Two kinds of high efficient Agl pyrotechnics BR-88-5 and BR-91-Y have been developed.The tests in the cloud chamber show that the AgI ice nucleating effectiveness can reach up to 10^(15)/g,and the BR-91-Y has even higher ice nucleating rate.Two kinds of foreign AgI pyrotechnics have been made according to the given formulations and also tested in the cloud chamber for comparison.X-ray diffraction analysis for the aerosols produced by burning BR-91-Y shows that AgI in acrosols still retains the hexagonal crystal form and the lattice parameters are smaller than those of pure AgI and other AgI composite nuclei,and closer to ice.Combining with the other tests,the reasons for the high effi- ciency of BR-91-Y have been discussed.